U.S. patent number 8,310,107 [Application Number 12/237,450] was granted by the patent office on 2012-11-13 for power transmission control device, power transmitting device, non-contact power transmission system, and secondary coil positioning method.
This patent grant is currently assigned to Seiko Epson Corporation. Invention is credited to Mikimoto Jin.
United States Patent |
8,310,107 |
Jin |
November 13, 2012 |
Power transmission control device, power transmitting device,
non-contact power transmission system, and secondary coil
positioning method
Abstract
A power transmission control device used for a non-contact power
transmission system includes a power-transmitting-side control
circuit that controls power transmission to a power receiving
device, and a harmonic detection circuit that detects a harmonic
signal of a drive frequency of a primary coil. A resonant circuit
(leakage inductance and resonant capacitor) that resonates with the
harmonic of the drive frequency of the primary coil L1 is formed in
the power receiving device so that harmonic resonance occurs. The
harmonic detection circuit detects the harmonic resonance peak of
the drive frequency of the primary coil.
Inventors: |
Jin; Mikimoto (Chino,
JP) |
Assignee: |
Seiko Epson Corporation (Tokyo,
JP)
|
Family
ID: |
40470874 |
Appl.
No.: |
12/237,450 |
Filed: |
September 25, 2008 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20090079271 A1 |
Mar 26, 2009 |
|
Foreign Application Priority Data
|
|
|
|
|
Sep 26, 2007 [JP] |
|
|
2007-249444 |
|
Current U.S.
Class: |
307/104;
320/108 |
Current CPC
Class: |
H02J
50/12 (20160201); H02J 50/70 (20160201); H02J
50/80 (20160201); H02J 7/00045 (20200101); H02J
50/90 (20160201); H02J 50/60 (20160201) |
Current International
Class: |
H01F
27/42 (20060101); H03K 3/64 (20060101) |
Field of
Search: |
;307/104 ;320/108 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
A-6-4723 |
|
Jan 1994 |
|
JP |
|
A-08-033112 |
|
Feb 1996 |
|
JP |
|
A-9-182212 |
|
Jul 1997 |
|
JP |
|
A-9-215211 |
|
Aug 1997 |
|
JP |
|
A-2001-309579 |
|
Nov 2001 |
|
JP |
|
A-2002-101578 |
|
Apr 2002 |
|
JP |
|
A-2002-152997 |
|
May 2002 |
|
JP |
|
A-2003-284264 |
|
Oct 2003 |
|
JP |
|
A-2005-6440 |
|
Jan 2005 |
|
JP |
|
A-2005-6441 |
|
Jan 2005 |
|
JP |
|
A-2005-6460 |
|
Jan 2005 |
|
JP |
|
A-2006-500894 |
|
Jan 2006 |
|
JP |
|
A-2006-60909 |
|
Mar 2006 |
|
JP |
|
A-2006-320047 |
|
Nov 2006 |
|
JP |
|
A-2008-036101 |
|
Feb 2008 |
|
JP |
|
Other References
US. Appl. No. 12/237,733; in the name of Mikimoto Jin, filed Sep.
25, 2008. cited by other .
U.S. Appl. No. 12/236,192; in the name of Mikimoto Jin, filed Sep.
23, 2008. cited by other .
U.S. Appl. No. 12/237,449; in the name of Mikimoto Jin, filed Sep.
25, 2008. cited by other.
|
Primary Examiner: Wallis; Michael Rutland
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. A power transmission control device that controls a power
transmitting device of a non-contact power transmission system, the
non-contact power transmission system transmitting power from the
power transmitting device to a power receiving device via
non-contact power transmission through a primary coil and a
secondary coil that are electromagnetically coupled, the power
transmission control device comprising: a power-transmitting-side
control circuit that controls power transmission of the power
transmitting device to the power receiving device; and a harmonic
detection circuit that detects a harmonic of a drive signal of the
primary coil, a resonant circuit being formed when the primary coil
and the secondary coil are electromagnetically coupled in a state
in which the primary coil and the secondary coil have a given
positional relationship, the resonant circuit resonating with the
harmonic of the drive signal of the primary coil; the harmonic
detection circuit detecting the harmonic of the drive signal of the
primary coil that occurs due to resonance of the resonant circuit;
and the power-transmitting-side control circuit detecting that the
primary coil and the secondary coil have the given positional
relationship based on a detection result of the harmonic detection
circuit.
2. The power transmission control device as defined in claim 1, the
resonant circuit being formed by a leakage inductance and a
capacitor connected to the secondary coil when the primary coil and
the secondary coil are electromagnetically coupled in a state in
which a position of the primary coil coincides with a position of
the secondary coil in a plan view, the resonant circuit resonating
with the harmonic of the drive signal of the primary coil; and the
harmonic detection circuit operating as a position detection
circuit that detects that the position of the primary coil
coincides with the position of the secondary coil in the plan
view.
3. The power transmission control device as defined in claim 1, the
resonant circuit being formed by a leakage inductance and a
capacitor connected to the secondary coil when the primary coil and
the secondary coil are electromagnetically coupled in a state in
which the center of the primary coil and the center of the
secondary coil are positioned at a given distance, the resonant
circuit resonating with the harmonic of the drive signal of the
primary coil; and the harmonic detection circuit operating as a
position detection circuit that detects that the primary coil and
the secondary coil are positioned at the given distance.
4. The power transmission control device as defined in claim 1,
further comprising: an actuator control circuit that controls the
operation of an actuator, the actuator moving a position of the
primary coil in an XY plane, the primary coil being moved by
causing the actuator control circuit to drive the actuator using a
detection output from the harmonic detection circuit as an index to
position the primary coil with the secondary coil.
5. The power transmission control device as defined in claim 1,
further comprising: an approach detection circuit that detects the
approach of the secondary coil based on a coil end voltage or a
coil current of the primary coil.
6. The power transmission control device as defined in claim 5, the
secondary coil being a secondary coil provided with a magnetic
material, and the approach detection circuit detecting the approach
of the secondary coil by detecting a decrease of the coil end
voltage or the coil current when driving the primary coil at a
given frequency, the decrease being caused by an increase of
inductance of the primary coil with the approach of the secondary
coil provided with the magnetic material.
7. The power transmission control device as defined in claim 5, the
power-transmitting-side control circuit intermittently driving the
primary coil at a given frequency in order to detect the approach
of the secondary coil.
8. The power transmission control device as defined in claim 1,
further comprising: a notification section that indicates a
detection result of the relative positional relationship between
the primary coil and the secondary coil based on a detection output
from the harmonic detection circuit.
9. A power transmitting device comprising: the power transmission
control device as defined in claim 1; and a primary coil.
10. A non-contact power transmission system comprising: the power
transmitting device as defined in claim 9; and a power receiving
device that includes a resonant circuit, the resonant circuit
resonating with a harmonic of the drive signal of a primary
coil.
11. A secondary coil positioning method for a non-contact power
transmission system that transmits power from a power transmitting
device having a primary coil to a power receiving device having a
secondary coil via non-contact power transmission through the
primary coil and the secondary coil that are electromagnetically
coupled, a capacitor being connected to the secondary coil, and a
resonant circuit that resonates with a harmonic of a drive signal
of the primary coil being formed by a leakage inductance and the
capacitor when the primary coil and the secondary coil are
electromagnetically coupled in a state in which a position of the
primary coil coincides with a position of the secondary coil in a
plan view, the method comprising: providing a harmonic detection
circuit and a notification section in the power transmitting
device, the harmonic detection circuit detecting the harmonic of
the drive signal of the primary coil that occurs due to resonance
of the resonant circuit; and the notification section indicating a
detection result for the relative positional relationship between
the primary coil and the secondary coil based on a detection output
from the harmonic detection circuit; and moving the position of the
power receiving device using notification information from the
notification section as an index to position the secondary coil
with respect to the primary coil.
Description
Japanese Patent Application No. 2007-249444 filed on Sep. 26, 2007,
is hereby incorporated by reference in its entirety.
BACKGROUND
The present invention relates to a power transmission control
device, a power transmitting device, a non-contact power
transmission system, a secondary coil positioning method, and the
like.
In recent years, non-contact power transmission (contactless power
transmission) that utilizes electromagnetic induction to enable
power transmission without metal-to-metal contact has attracted
attention. As application examples of non-contact power
transmission, charging a portable telephone, charging a household
appliance (e.g., cordless telephone handset or watch), and the like
have been proposed.
JP-A-2006-60909 discloses a non-contact power transmission device
using a primary coil and a secondary coil, for example.
JP-A-2005-6460 discloses technology that detects misalignment of a
primary coil and a secondary coil in a non-contact power
transmission system. According to the technology disclosed in
JP-A-2005-6460, whether or not the relative positional relationship
between the primary coil and the secondary coil is correct is
detected based on an output voltage of a rectifier circuit of a
power receiving device. When the relative positional relationship
between the primary coil and the secondary coil is correct, a
light-emitting diode (LED) is turned ON to notify the user that the
relative positional relationship between the primary coil and the
secondary coil is correct.
According to the technology disclosed in JP-A-2005-6460, the user
can be notified whether or not the primary coil and the secondary
coil are accurately positioned. However, since occurrence of
mispositioning is determined based on the output from the rectifier
circuit of the power receiving device, power must be continuously
transmitted from the power transmitting device to the power
receiving device. Moreover, the power transmitting device cannot
voluntarily acquire coil misalignment information.
SUMMARY
According to one aspect of the invention, there is provided a power
transmission control device that controls a power transmitting
device of a non-contact power transmission system, the non-contact
power transmission system transmitting power from the power
transmitting device to a power receiving device via non-contact
power transmission through a primary coil and a secondary coil that
are electromagnetically coupled, the power transmission control
device comprising:
a power-transmitting-side control circuit that controls power
transmission of the power transmitting device to the power
receiving device; and
a harmonic detection circuit that detects a harmonic signal of a
drive signal of the primary coil.
According to another aspect of the invention, there is provided a
power transmitting device comprising:
the above power transmission control device; and
a primary coil.
According to another aspect of the invention, there is provided a
non-contact power transmission system comprising:
the above power transmitting device; and
a power receiving device that includes a resonant circuit, the
resonant circuit resonating with a harmonic of the drive signal of
a primary coil.
According to another aspect of the invention, there is provided a
secondary coil positioning method for a non-contact power
transmission system that transmits power from a power transmitting
device to a power receiving device via non-contact power
transmission through a primary coil and a secondary coil that are
electromagnetically coupled, a capacitor being connected to the
secondary coil, and a resonant circuit that resonates with a
harmonic of a drive frequency of the primary coil being formed by a
leakage inductance and the capacitor when the primary coil and the
secondary coil are electromagnetically coupled in a state in which
the center of the primary coil coincides with the center of the
secondary coil, the method comprising:
providing a harmonic detection circuit and a notification section
in the power transmitting device, the harmonic detection circuit
detecting a harmonic signal of a drive frequency of the primary
coil provided in the power transmitting device, and the
notification section indicating a detection result for the relative
positional relationship between the primary coil and the secondary
coil based on a detection output from the harmonic detection
circuit; and
moving the position of the power receiving device using
notification information from the notification section as an index
to position the secondary coil with respect to the primary
coil.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are views showing an example of an application of a
non-contact power transmission system utilizing the invention.
FIG. 2 is a circuit diagram showing an example of a specific
configuration of each section of a non-contact power transmission
system that includes a power transmitting device and a power
receiving device.
FIGS. 3A and 3B are views illustrative of the principle of
information transmission between a primary-side instrument and a
secondary-side instrument.
FIG. 4 is a view showing a primary-side (power transmitting device)
configuration for secondary-side instrument approach detection and
automatic coil positioning.
FIGS. 5A to 5F are views illustrative of an increase in inductance
that occurs when a magnetic material attached to a secondary coil
has approached a primary coil.
FIGS. 6A to 6D are views showing examples of the relative
positional relationship between a primary coil and a secondary
coil.
FIG. 7 is a view showing the relationship between the relative
distance between a primary coil and a secondary coil and the
inductance of the primary coil.
FIG. 8 is a view illustrative of the concept of a leakage
inductance in a transformer formed by electromagnetically coupling
a primary coil and a secondary coil.
FIGS. 9A to 9E are views illustrative of the configuration and the
operation of a harmonic resonant circuit.
FIGS. 10A and 10B are views illustrative of a harmonic resonant
circuit that resonates when a primary coil and a secondary coil are
positioned at a given distance R.
FIGS. 11A to 11D are views illustrative of a position at which the
harmonic resonance peak is obtained when scanning a primary coil
with respect to a secondary coil.
FIG. 12 is a view showing an example of a change in inductance of a
primary coil and an example of a change in harmonic voltage
obtained from a harmonic detection circuit when a primary coil
approaches a secondary coil.
FIGS. 13A and 13B are views illustrative of a harmonic resonant
circuit that resonates when the position of a primary coil
coincides with the position of a secondary coil.
FIGS. 14A and 14B are views illustrative of a primary coil
positioning method that scans a primary coil by trial and error
using a detection output from a harmonic resonant circuit as an
index.
FIG. 15 is a flowchart showing a process of scanning a primary coil
using a harmonic detection output as an index.
FIG. 16 is a perspective view showing the basic configuration of an
XY stage.
FIG. 17 is a view showing another configuration of a power
transmitting device (configuration that detects the approach of a
secondary-side instrument and notifies the user of coil relative
positional relationship information).
FIGS. 18A and 18B are views showing an example of an application of
a non-contact power transmission system using a power transmitting
device having a configuration shown in FIG. 17.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
Several embodiments of the invention may enable a power
transmitting device (primary-side instrument) to voluntarily and
accurately detect the relative positional relationship between the
power transmitting device (primary-side instrument) and a power
receiving device (secondary-side instrument).
(1) According to one embodiment of the invention, there is provided
a power transmission control device that controls a power
transmitting device of a non-contact power transmission system, the
non-contact power transmission system transmitting power from the
power transmitting device to a power receiving device via
non-contact power transmission through a primary coil and a
secondary coil that are electromagnetically coupled, the power
transmission control device comprising:
a power-transmitting-side control circuit that controls power
transmission of the power transmitting device to the power
receiving device; and
a harmonic detection circuit that detects a harmonic signal of a
drive signal (drive frequency) of the primary coil.
According to this embodiment, the harmonic detection circuit
provided in the power transmission control device detects the
harmonic resonance peak of the drive frequency of the primary coil.
For example, a resonant circuit that resonates with the harmonic of
the drive frequency of the primary coil is formed in the
secondary-side instrument (power receiving device side).
For example, the secondary-side resonant circuit is formed when the
primary coil and the secondary coil have a given relative
positional relationship so that the resonance peak occurs. For
example, a situation in which the primary coil and the secondary
coil have a given relative positional relationship can be
accurately detected irrespective of the operation of the
secondary-side instrument (i.e., the primary-side instrument can
voluntarily detect the situation) by intermittently driving the
primary coil and monitoring the detection output level of the
harmonic detection circuit.
For example, when the resonance frequency of the primary-side
resonant circuit including the primary coil is referred to as fp,
the drive frequency of the primary coil is generally set at a
frequency (fd) away from the resonance frequency (fp) taking the
operational stability into consideration.
When the drive signal of the primary coil is a symmetrical
alternating-current signal, the harmonic (fs) of the drive
frequency of the primary coil is only an odd-order harmonic. For
example, the fifth-order harmonic (fs=5fd) may be used to detect
the positional relationship between the primary coil (power
transmitting device) and the secondary coil (power receiving device
or secondary-side instrument).
Since the harmonic signal has a frequency that is not involved in
normal power transmission from the primary coil to the secondary
coil, the harmonic signal does not affect the normal operation.
Moreover, since the resonance energy is reduced to about 1/nth of
the basic frequency when using an nth-order (n is an odd number
equal to or larger than three, for example) harmonic, the resonance
peak value has an appropriate level so that the harmonic resonance
peak can be easily detected by the harmonic detection circuit.
The detection output of the harmonic detection circuit may be used
to detect the positions of the primary coil (power transmitting
device) and the secondary coil (power receiving device or
secondary-side instrument) in a broad sense. The detection output
may be utilized for various applications. For example, the primary
coil and the secondary coil may be positioned using the detection
output of the harmonic detection circuit as an index.
A situation in which the secondary-side instrument has been placed
at a given position can be detected utilizing the harmonic
detection output (secondary-side instrument placement
detection).
A situation in which the primary coil or the secondary coil moves
away (or approaches) can be detected in real time by monitoring a
change in the level of the harmonic detection output (detection of
movement, approach, leave, or the like).
A situation in which the secondary-side instrument has been removed
can be detected when the harmonic detection output at a given level
has not been obtained (leave detection).
When the harmonic can be detected, it can be determined that the
article placed in the placement area is not a screw, a nail, or the
like, but is a secondary-side instrument that can be (may be) a
power transmission target. Specifically, the harmonic detection
circuit also has a function of a means that detects whether or not
the article placed in the placement area is an instrument that can
be a power transmission target (i.e., a detector that detects
whether or not the article is an appropriate secondary-side
instrument).
(2) In the power transmission control device,
a resonant circuit may be formed in the power receiving device, the
resonant circuit resonating with a harmonic of the drive signal of
the primary coil; and
the harmonic detection circuit may detect a harmonic resonance
signal of the resonant circuit.
According to this embodiment, the resonant circuit that resonates
with the harmonic of the drive frequency of the primary coil is
formed in the power receiving device so that the harmonic resonance
peak is obtained. The resonant circuit may be implemented by
setting the capacitance of the resonant capacitor connected to the
secondary coil to resonate with a leakage inductance when the
primary coil and the secondary coil are positioned at a given
distance R (R.gtoreq.0), for example.
(3) In the power transmission control device,
the power receiving device may include a capacitor connected to the
secondary coil;
a resonant circuit may be formed by a leakage inductance and the
capacitor when the primary coil and the secondary coil are
electromagnetically coupled in a state in which the center of the
primary coil coincides with the center of the secondary coil, the
resonant circuit resonating with a harmonic of the drive signal of
the primary coil; and
the harmonic detection circuit may operate as a position detection
circuit that detects that a position of the primary coil coincides
with a position of the secondary coil.
According to this embodiment, the resonant circuit is formed by the
capacitor and the leakage inductance when the position of the
primary coil coincides with the position of the secondary coil.
Therefore, the detection output from the harmonic detection circuit
can be utilized as a position detection signal that indicates that
the position of the primary coil coincides with the position of the
secondary coil. Therefore, the primary coil and the secondary coil
can be positioned using the level of the harmonic detection output
as the position detection signal as an index.
For example, an indicator lamp provided in the primary-side
instrument is turned ON when a harmonic detection output that
exceeds a given level is obtained. The user manually moves the
secondary-side instrument by trial and error to search for a
position at which the lamp is turned ON, for example. This enables
the secondary coil to be positioned with respect to the primary
coil.
(4) In the power transmission control device,
the power receiving device may include a capacitor connected to the
secondary coil;
a resonant circuit may be formed by a leakage inductance and the
capacitor when the primary coil and the secondary coil are
electromagnetically coupled in a state in which the center of the
primary coil and the center of the secondary coil are positioned at
a given distance, the resonant circuit resonating with a harmonic
of the drive signal of the primary coil; and
the harmonic detection circuit may operate as a position detection
circuit that detects that the primary coil and the secondary coil
are positioned at the given distance.
According to this embodiment, the resonant circuit is formed by the
capacitor and the leakage inductance when the primary coil and the
secondary coil are positioned at the given distance. Therefore, the
detection output from the harmonic detection circuit can be
utilized as a position detection signal that indicates that the
primary coil and the secondary coil are positioned at the given
distance.
Therefore, a given relative positional relationship between the
primary coil and the secondary coil may be detected, or the primary
coil and the secondary coil can be set to have the given relative
positional relationship using the level of the harmonic detection
output as the position detection signal as an index.
(5) The power transmission control device may further comprise:
an actuator control circuit that controls the operation of an
actuator, the actuator moving a position of the primary coil in an
XY plane, and
the primary coil may be moved by causing the actuator control
circuit to drive the actuator using a detection output from the
harmonic detection circuit as an index to position the primary coil
with the secondary coil.
According to this embodiment, the position of the primary coil is
moved by trial and error using the actuator until a harmonic
detection output equal to or higher than a given level is obtained,
for example. This automatically implements a given relative
positional relationship between the primary coil and the secondary
coil.
The primary coil may be moved by trial and error by moving the
primary coil based on a given movement sequence (e.g., based on a
spiral scan sequence), or moving the primary coil at random, for
example.
(6) The power transmission control device may further comprise:
an approach detection circuit that detects the approach of the
secondary coil based on a coil end voltage or a coil current of the
primary coil.
According to this configuration, the approach of the secondary coil
(to the primary coil) can be automatically detected while detecting
the relative positional relationship between the primary coil and
the secondary coil based on the harmonic detection output.
Therefore, the relative positional relationship between the primary
coil and the secondary coil can be automatically detected using
detection of the approach of the secondary coil as a trigger, for
example, whereby the convenience of the non-contact power
transmission system is improved.
When the approach of the secondary coil can be detected, it can be
determined that the secondary-side instrument that can be a power
transmission target has approached. Therefore, the approach
detection circuit also has a function of a means that detects
whether or not the instrument placed in the placement area is a
secondary-side instrument that includes the secondary coil and can
be a power transmission target (i.e., a detector that detects
whether or not the instrument is an appropriate secondary-side
instrument).
(7) In the power transmission control device,
the secondary coil may be a secondary coil provided with a magnetic
material, and
the approach detection circuit may detect the approach of the
secondary coil by detecting a decrease of the coil end voltage or
the coil current when driving the primary coil at a given
frequency, the decrease being caused by an increase of inductance
of the primary coil with the approach of the secondary coil
provided with the magnetic material.
This embodiment provides an example of a specific secondary coil
approach detection method. The secondary coil is a coil provided
with a magnetic material. The magnetic material is a shield that
separates a magnetic flux of the secondary coil from a
secondary-side circuit, or may be a core of the secondary coil, for
example.
When the secondary coil has approached the primary coil, a magnetic
flux of the primary coil passes through the magnetic material of
the secondary coil. As a result, the inductance of the primary coil
increases. The term "inductance" used herein refers to an
inductance (more accurately an apparent inductance) that changes
due to the approach of the secondary coil provided with the
magnetic material. The term "apparent inductance" is distinguished
from the inductance (self-inductance) of the primary coil (i.e.,
the inductance of the primary coil when the primary coil is not
affected by the secondary coil). The value of the apparent
inductance is obtained by measuring the inductance of the primary
coil when the secondary coil has approached the primary coil using
a measuring instrument, for example.
In this specification, the term "apparent inductance" is merely
written as "inductance", except for the case where clear statement
of the term "apparent inductance" is considered to be necessary.
Since the coil end voltage (coil current) of the primary coil
decreases due to an increase in the inductance of the primary coil,
the approach of the primary coil can be detected by detecting the
change in the coil end voltage (coil current).
(8) In the power transmission control device,
the power-transmitting-side control circuit may intermittently
drive the primary coil at a given frequency in order to detect the
approach of the secondary coil.
The primary coil is intermittently (e.g., cyclically) driven at a
given frequency in order to automatically detect the approach of
the secondary coil. In this case, the approach of the secondary
coil is detected when a decrease in the coil end voltage (coil
current) has been detected.
(9) The power transmission control device may further comprise:
notification section that indicates a detection result of the
relative positional relationship between the primary coil and the
secondary coil based on a is detection output from the harmonic
detection circuit.
According to this embodiment, the notification section notifies the
user of the detection result for the relative positional
relationship between the primary coil and the secondary coil by
appealing to the senses (e.g., sight or hearing) of the user. This
enables the user to determine of the positional relationship
between the primary coil and the secondary coil.
Moreover, placement or removal (leave) of the secondary-side
instrument can also be detected. The notification section may
notify the user whether or not the secondary-side instrument is an
instrument that can be a power transmission target (e.g., a
secondary-side instrument having a secondary-side configuration
compliant with the standard).
Notification may be implemented in various ways. For example, a
multi-stage notification operation may be performed corresponding
to the level of the harmonic detection output as a coil relative
positional relationship detection signal.
For example, a red indicator lamp may be turned ON when a harmonic
detection output that exceeds a first level is obtained, and a
green indicator lamp may be turned ON when a harmonic detection
output that exceeds a second level higher than the first level is
obtained. If the user manually moves the secondary-side instrument
by trial and error and checks whether or not the lamp is turned ON
and the color of the lamp, the secondary coil can be more
efficiently positioned with respect to the primary coil.
Specifically, since the secondary coil has approached the primary
coil to some extent when the red lamp is turned ON, the user can
more carefully move the secondary-side instrument within a narrow
search (movement) range. This enables the secondary coil to be
easily positioned with respect to the primary coil.
In addition, positioning is further facilitated by forming a
transparent placement area so that the user can visually observe
the position of the coil provided under the placement area either
directly or indirectly, for example.
(10) According to another embodiment of the invention, there is
provided a power transmitting device comprising:
one of the above power transmission control devices; and
a primary coil.
This implements a novel power transmitting device for a novel
non-contact power transmission system that has a function of
voluntarily detecting the positional relationship between the
primary coil and the secondary coil.
(11) According to another embodiment of the invention, there is
provided a non-contact power transmission system comprising:
the above power transmitting device; and
a power receiving device that includes a resonant circuit, the
resonant circuit resonating with a harmonic of the drive signal of
a primary coil.
This automatically implements a novel non-contact power
transmission system that can detect the positional relationship
between the primary coil and the secondary coil using the harmonic
detection circuit provided in the primary-side instrument.
(12) According to another embodiment of the invention, there is
provided a secondary coil positioning method for a non-contact
power transmission system that transmits power from a power
transmitting device to a power receiving device via non-contact
power transmission through a primary coil and a secondary coil that
are electromagnetically coupled, a capacitor being connected to the
secondary coil, and a resonant circuit that resonates with a
harmonic of a drive frequency of the primary coil being formed by a
leakage inductance and the capacitor when the primary coil and the
secondary coil are electromagnetically coupled in a state in which
the center of the primary coil coincides with the center of the
secondary coil, the method comprising:
providing a harmonic detection circuit and a notification section
in the power transmitting device, the harmonic detection circuit
detecting a harmonic signal of a drive frequency of the primary
coil provided in the power transmitting device, and the
notification section indicating a detection result for the relative
positional relationship between the primary coil and the secondary
coil based on a detection output from the harmonic detection
circuit; and
moving the position of the power receiving device using
notification information from the notification section as an index
to position the secondary coil with respect to the primary
coil.
According to this embodiment, an indicator lamp is turned ON when a
harmonic detection output that exceeds a given level is obtained,
for example. The user manually moves the secondary-side instrument
by trial and error to search for a position at which the lamp is
turned ON so that the secondary coil can be positioned with respect
to the primary coil.
Preferred embodiments of the invention are described below with
reference to the drawings. Note that the following embodiments do
not in any way limit the scope of the invention defined by the
claims laid out herein. Note that all elements of the following
embodiments should not necessarily be taken as essential
requirements for the invention.
The principle of detecting the relative positional relationship
between a primary coil and a secondary coil using harmonic
detection is described below with reference to an example in which
the position of the primary coil is automatically moved using the
output from a harmonic detection circuit. Various variations
utilizing the harmonic detection output (e.g., a configuration that
notifies the user of the detected positional relationship between
the primary coil and the secondary coil, and an example in which a
secondary-side instrument is moved manually) are described
thereafter.
First Embodiment
An application example of a non-contact power transmission system
utilizing the invention is given below.
Application Example of Non-Contact Power Transmission System
FIGS. 1A and 1B are views showing an example of an application of a
non-contact power transmission system utilizing the invention. FIG.
1A is a perspective view showing a system desk, and FIG. 1B is a
cross-sectional view of the system desk shown in FIG. 1A along the
line P-P'.
As shown in FIG. 1B, a power-transmitting-side device (i.e., a
primary-side structure including a power transmitting device 10
according to the invention, an actuator (not shown), and an XY
stage 702) 704 is provided in a structure (system desk in this
example) 620 having a flat surface.
Specifically, the power-transmitting-side device 704 is placed in a
depression formed in the system desk 620. A flat plate (flat
member; e.g., an acrylic plate having a thickness of several
millimeters) 600 is provided over (on the upper side of) the system
desk 620. The flat plate 600 is supported by a support member
610.
The flat plate 600 includes a portable terminal placement area Z1
in which a portable terminal (such as a portable telephone
terminal, a PDA terminal, and a portable computer terminal) is
placed.
As shown in FIG. 1A, the portable terminal placement area
(placement area) Z1 included in the flat plate 600 differs in color
from the remaining area so that the user can determine that the
portable terminal placement area Z1 is an area in which a portable
terminal should be placed. Note that the color of the boundary area
between the portable terminal placement area (placement area) Z1
and the remaining area may be changed instead of changing the color
of the entire portable terminal placement area Z1.
The placement area Z1 may be formed using a transparent member, and
the area other than the placement area Z1 may be formed using an
opaque member. In this case, since the user can determine the
placement area and visually observe the lower side (inside) of the
placement area, the user can easily determine the position of a
primary coil provided under the placement area either directly or
indirectly. Therefore, when the user moves the position of a
secondary-side instrument to position a primary coil and a
secondary coil, the user can more easily position the primary coil
and the secondary coil so that the convenience to the user is
improved.
A portable terminal (secondary-side instrument) 510 includes a
power receiving device 40 (including a secondary coil) that
receives power transmitted from the power transmitting device
10.
When the portable terminal 510 has been placed at an approximate
position in the portable terminal placement area Z1, the power
transmitting device 10 provided in the system desk 620
automatically detects that the portable terminal 510 has been
placed in the portable terminal placement area Z1, and moves the XY
stage (movable stage) by driving the actuator (not shown in FIG. 1)
to automatically adjust the position of the primary coil
corresponding to the position of the secondary coil. The
above-described primary coil position automatic adjustment function
enables non-contact power transmission to be performed while
optimizing the positional relationship between the primary coil and
the secondary coil regardless of the manufacturer, type, size,
shape, design, and the like of the portable terminal.
Configuration and Operation of Non-Contact Power Transmission
System
FIG. 2 is a circuit diagram showing an example of a specific
configuration of each section of a non-contact power transmission
system that includes a power transmitting device and a power
receiving device.
Configuration and Operation of Power Transmitting Device
As shown in FIG. 2 (left), the power-transmitting-side device
(primary-side structure) 704 includes the XY stage (movable stage)
702, the power transmitting device 10 that can be moved by the XY
stage 702 in an X-axis direction and a Y-axis direction, an
actuator driver 710, an X-direction actuator 720, and a Y-direction
actuator 730. Specifically, the power transmitting device 10 is
placed on a top plate (movable plate) of the XY stage 702
(described later with reference to FIG. 14).
The power transmitting device 10 includes a power transmission
control device 20, a power transmitting section 12, a waveform
monitoring circuit 14, and a display section 16 as a notification
means. The power transmission control device 20 includes a
power-transmitting-side control circuit 22, a drive clock signal
generation circuit 23, an oscillation circuit 24, a harmonic
detection circuit 25 (including a filter circuit 27, a mixer 29
that adds a harmonic fs, and a detection circuit (waveform
detection circuit) 31), a driver control circuit 26, a waveform
detection circuit (peak-hold circuit or pulse width detection
circuit) 28, comparators (CP1 and CP2), and an actuator control
circuit 37.
The power receiving device 40 includes a power receiving section
42, a load modulation section 46, and a power supply control
section 48. The power receiving section 42 includes a rectifier
circuit 43, a load modulation section 46, a power supply control
section 48, and a control section 50, A load 90 includes a charge
control device 92 and a battery (secondary battery) 94.
The configuration shown in FIG. 2 implements a non-contact power
transmission (contactless power transmission) system that
electromagnetically couples the primary coil L1 and the secondary
coil L2 to transmit power from the power transmitting device 10 to
the power receiving device 40 and supply power (voltage VOUT) to
the load 90 from a voltage output node NB6 of the power receiving
device 40.
The power transmitting section 12 generates an alternating-current
voltage having a given frequency during power transmission, and
generates an alternating-current voltage having a frequency that
differs depending on data during data transfer. The power
transmitting section 12 supplies the generated alternating-current
voltage to the primary coil L1.
FIGS. 3A and 3B are views illustrative of the principle of
information transmission between a primary-side instrument and a
secondary-side instrument. Information is transmitted from the
primary-side instrument to the secondary-side instrument utilizing
frequency modulation. Information is transmitted from the
secondary-side instrument to the primary-side instrument utilizing
load modulation.
As shown in the FIG. 3A, the power transmitting device 10 generates
an alternating-current voltage having a frequency f1 when
transmitting data "1" to the power receiving device 40, and
generates an alternating-current voltage having a frequency f2 when
transmitting data "0" to the power receiving device 40, for
example.
As shown in FIG. 3B, the power receiving device 40 can switch the
load state between a low-load state and a high-load state by load
modulation to transmit data "0" or "1" to the primary-side
instrument (power transmitting device 10).
The power transmitting section 12 shown in FIG. 2 may include a
first power transmitting driver that drives one end of the primary
coil L1, a second power transmitting driver that drives the other
end of the primary coil L1, and at least one capacitor that forms a
resonant circuit with the primary coil L1. Each of the first and
second power transmitting drivers included in the power
transmitting section 12 is an inverter circuit (or buffer circuit)
that includes a power MOS transistor, for example, and is
controlled by the driver control circuit 26 of the power
transmission control device 20.
The primary coil L1 (power-transmitting-side coil) is
electromagnetically coupled to the secondary coil L2
(power-receiving-side coil) to form a power transmission
transformer. For example, when power transmission is necessary, the
portable telephone 510 is placed on the flat plate 600 so that a
magnetic flux of the primary coil L1 passes through the secondary
coil L2, as shown in FIG. 1. When power transmission is
unnecessary, the portable telephone 510 is physically separated
from the flat plate 600 so that a magnetic flux of the primary coil
L1 does not pass through the secondary coil L2.
As the primary coil L1 and the secondary coil L2, a planar coil
formed by spirally winding an insulated wire in a single plane may
be used, for example. Note that a planar coil formed by spirally
winding a twisted wire (i.e., a wire obtained by twisting a
plurality of insulated thin wires) may also be used. The type of
coil is not particularly limited.
The waveform monitoring circuit 14 is a circuit that detects an
induced voltage in the primary coil L1. The waveform monitoring
circuit 14 may include resistors RA1 and RA2, and a diode DA1
provided between a common connection point NA3 of the resistors RA1
and RA2 and a power supply GND (low-potential-side power supply in
a broad sense), for example. Specifically, a signal PHIN obtained
by dividing the induced voltage in the primary coil L1 using the
resistors RA1 and RA2 is input to the waveform detection circuit 28
of the power transmission control device 20.
The display section 16 displays the state (e.g., power transmission
or ID authentication) of the non-contact power transmission system
using a color, an image, or the like. The display section 16 is
implemented by a light-emitting diode (LED), a liquid crystal
display (LCD), or the like.
The power transmission control device 20 controls the power
transmitting device 10. The power transmission control device 20
may be implemented by an integrated circuit device (IC) or the
like. The power transmission control device 20 includes the
power-transmitting-side control circuit 22, the drive clock signal
generation circuit 23, the oscillation circuit 24, the harmonic
detection circuit 25, the driver control circuit 26, the waveform
detection circuit (peak-hold circuit or pulse width detection
circuit) 28, the comparators CP1 and CP2, and the actuator control
circuit 37.
The power-transmitting-side control circuit 22 controls the power
transmitting device 10 and the power transmission control device
20. The power-transmitting-side control circuit 22 may be
implemented by a gate array, a microcomputer, or the like.
Specifically, the power-transmitting-side control circuit 22
performs sequence control and a determination process necessary for
power transmission, load detection, frequency modulation, foreign
object detection, removal (detachment) detection, and the like.
The oscillation circuit 24 includes a crystal oscillation circuit
or the like, and generates a primary-side clock signal. The drive
clock signal generation circuit 23 generates a drive control signal
having a desired frequency based on a clock signal generated by the
oscillation circuit 24 and a frequency setting signal supplied from
the power-transmitting-side control circuit 22.
The driver control circuit 26 outputs the drive control signal to
the power transmitting drivers (not shown) of the power
transmitting section 12 while preventing a situation in which the
power transmitting drivers (not shown) are turned ON simultaneously
to control the operations of the power transmitting driver, for
example.
The waveform detection circuit 28 monitors the waveform of the
signal PHIN that corresponds to an induced voltage at one end of
the primary coil L1, and performs load detection, foreign object
detection, and the like. For example, when the load modulation
section 46 of the power receiving device 40 has performed load
modulation for transmitting data to the power transmitting device
10, the signal waveform of the induced voltage in the primary coil
L1 changes correspondingly.
As shown in FIG. 3B, the amplitude (peak voltage) of the signal
waveform decreases when the load modulation section 46 of the power
receiving device 40 reduces the load in order to transmit data "0",
and increases when the load modulation section 46 increases the
load in order to transmit data "1". Therefore, the waveform
detection circuit 28 can determine whether the data transmitted
from the power receiving device 40 is "0" or "1" by determining
whether or not the peak voltage has exceeded a threshold voltage by
performing a peak-hold process on the signal waveform of the
induced voltage, for example. Note that the waveform detection
method is not limited to the above-described method. For example,
the waveform detection circuit 28 may determine whether the
power-receiving-side load has increased or decreased utilizing a
physical quantity other than the peak voltage. For example, whether
the power-receiving-side load has increased or decreased may be
determined utilizing the peak current.
As the waveform detection circuit 28, a peak-hold circuit (or a
pulse width detection circuit that detects the pulse width
determined by the phase difference between a voltage and a current)
may be used.
Configuration and Operation of Power Receiving Device
The power receiving device 40 (power receiving module or secondary
module) may include the secondary coil L2 (including a resonant
capacitor C2 connected to each end, and preferably including a
magnetic material FS), the power receiving section 42, the load
modulation section 46, the power supply control section 48, and a
power reception control device 50. Note that the power receiving
device 40 and the power reception control device 50 are not limited
to the configuration shown in FIG. 2. Various modifications may be
made such as omitting some of the elements, adding other elements,
or changing the connection relationship.
The power receiving section 42 converts an alternating-current
induced voltage in the secondary coil L2 into a direct-current
voltage. A rectifier circuit 43 included in the power receiving
section 42 converts the alternating-current induced voltage. The
rectifier circuit 43 includes diodes DB1 to DB4. The diode DB1 is
provided between a node NB1 at one end of the secondary coil L2 and
a node NB3 (direct-current voltage VDC generation node). The diode
DB2 is provided between the node NB3 and a node NB2 at the other
end of the secondary coil L2. The diode DB3 is provided between the
node NB2 and a node NB4 (VSS). The diode DB4 is provided between
the nodes NB4 and NB1.
Resistors RB1 and RB2 of the power receiving section 42 are
provided between the nodes NB1 and NB4. A signal CCMPI obtained by
dividing the voltage between the nodes NB1 and NB4 using the
resistors RB1 and RB2 is input to a frequency detection circuit 60
of the power reception control device 50.
A capacitor CB1 and resistors RB4 and RB5 of the power receiving
section 42 are provided between the node NB3 (direct-current
voltage VDC) and the node NB4 (VSS). A divided voltage D4 obtained
by dividing the voltage between the nodes NB3 and NB4 using the
resistors RB4 and RB5 is input to a power-receiving-side control
circuit 52 and a position detection circuit 56 through a signal
line LP2. The divided voltage VD4 is input to the position
detection circuit 56 as a position detection signal input
(ADIN).
The load modulation section 46 performs a load modulation process.
Specifically, when the power receiving device 40 transmits desired
data to the power transmitting device 10, the load modulation
section 46 variably changes the load of the load modulation section
46 (secondary side) depending on the transmission target data to
change the signal waveform of the induced voltage in the primary
coil L1. The load modulation section 46 includes a resistor RB3 and
a transistor TB3 (N-type CMOS transistor) provided in series
between the nodes NB3 and NB4.
The transistor TB3 is ON/OFF-controlled based on a control signal
P3Q supplied from the power-receiving-side control circuit 52 of
the power reception control device 50 through a signal line LP3.
When performing the load modulation process by ON/OFF-controlling
the transistor TB3 and transmitting a signal to the power
transmitting device in an authentication stage before main power
transmission starts, a transistor TB2 of the power supply control
section 48 is turned OFF so that the load 90 is not electrically
connected to the power receiving device 40.
For example, when reducing the secondary-side load (high impedance)
in order to transmit data "0", the signal P3Q is set at the L level
so that the transistor TB3 is turned OFF. As a result, the load of
the load modulation section 46 becomes almost infinite (no load).
On the other hand, when increasing the secondary-side load (low
impedance) in order to transmit data "1", the signal P3Q is set at
the H level so that the transistor TB3 is turned ON. As a result,
the load of the load modulation section 46 is equivalent to the
resistor RB3 (high load).
The power supply control section 48 controls power supply to the
load 90. A regulator (LDO) 49 regulates the voltage level of the
direct-current voltage VDC obtained by conversion by the rectifier
circuit 43 to generate a power supply voltage VD5 (e.g., 5 V). The
power reception control device 50 operates based on the power
supply voltage VD5 supplied from the power supply control section
48, for example.
A switch circuit formed using a PMOS transistor (M1) is provided
between the input terminal and the output terminal of the regulator
(LDO) 49. A path that bypasses the regulator (LDO) 49 is formed by
causing the PMOS transistor (M1) (switch circuit) to be turned ON.
For example, since a power loss increases due to the equivalent
impedance of the regulator 49 and heat generation increases under
heavy load (e.g., when it is necessary to cause an almost constant
large current to steadily flow in the initial stage of charging a
secondary battery exhausted to a large extent), a current is
supplied to the load through a path that bypasses the
regulator.
An NMOS transistor (M2) and a pull-up resistor R8 that function as
a bypass control circuit are provided to ON/OFF-control the PMOS
transistor (M1) (switch circuit).
The NMOS transistor (M2) is turned ON when a high-level control
signal is supplied to the gate of the NMOS transistor (M2) through
a signal line LP4. This causes the gate of the PMOS transistor (M1)
to be set at a low level so that the PMOS transistor (M1) is turned
ON, whereby a path that bypasses the regulator (LDO) 49 is formed.
When the NMOS transistor (M2) is turned OFF, the gate of the PMOS
transistor (M1) is maintained at a high level through the pull-up
resistor R8. Therefore, the PMOS transistor (M1) is turned OFF so
that the bypass path is not formed.
The NMOS transistor (M2) is ON/OFF-controlled by the
power-receiving-side control circuit 52 included in the power
reception control device 50.
The transistor TB2 (P-type CMOS transistor) is provided between a
power supply voltage (VD5) generation node NB5 (output node of the
regulator 49) and the node NB6 (voltage output node of the power
receiving device 40), and is controlled based on a signal P1Q
output from the power-receiving-side control circuit 52 of the
power reception control device 50. Specifically, the transistor TB2
is turned ON when main power transmission is performed after
completion (establishment) of ID authentication.
The power reception control device 50 controls the power receiving
device 40. The power reception control device 50 may be implemented
by an integrated circuit device (IC) or the like. The power
reception control device 50 may operate based on the power supply
voltage VD5 generated based on the induced voltage in the secondary
coil L2. The power reception control device 50 may include the
(power-receiving-side) control circuit 52, the position detection
circuit 56, an oscillation circuit 58, the frequency detection
circuit 60, and a full-charge detection circuit 62.
The power-receiving-side control circuit 52 controls the power
receiving device 40 and the power reception control device 50. The
power-receiving-side control circuit 52 may be implemented by a
gate array, a microcomputer, or the like. The power-receiving-side
control circuit 52 operates based on a constant voltage (VD5) at
the output terminal of the series regulator (LDO) 49 as a power
supply voltage. The power supply voltage (VD5) is supplied to the
power-receiving-side control circuit 52 through a power supply line
LP1.
The power-receiving-side control circuit 52 performs sequence
control and a determination process necessary for ID
authentication, position detection, frequency detection,
full-charge detection, load modulation for authentication
communication, load modulation for communication that enables
detection of foreign object insertion, and the like.
The position detection circuit 56 monitors the waveform of the
signal ADIN that corresponds to the waveform of the induced voltage
in the secondary coil L2, and determines whether or not the
positional relationship between the primary coil L1 and the
secondary coil L2 is appropriate.
Specifically, the position detection circuit 56 converts the signal
ADIN into a binary value using a comparator, and determines whether
or not the positional relationship between the primary coil L1 and
the secondary coil L2 is appropriate.
The oscillation circuit 58 includes a CR oscillation circuit or the
like, and generates a secondary-side clock signal. The frequency
detection circuit 60 detects the frequency (f1 or f2) of the signal
CCMPI, and determines whether the data transmitted from the power
transmitting device 10 is "1" or "0".
The full-charge detection circuit 62 (charge detection circuit)
detects whether or not the battery 94 of the load 90 has been fully
charged (charge state). Specifically, the full-charge detection
circuit 62 detects the full-charge state by detecting whether a
light-emitting device (LEDR) used to indicate the charge state is
turned ON or OFF, for example. The full-charge detection circuit 62
determines that the battery 94 has been fully charged (charging has
been completed) when the light-emitting device (LEDR) has been
turned OFF for a given period of time (e.g., five seconds).
The charge control device 92 of the load 90 can also detect the
full-charge state based on the ON/OFF state of the light-emitting
device (LEDR).
The load 90 includes the charge control device 92 that controls
charging of the battery 94 and the like. The charge control device
92 detects the full-charge state based on the ON/OFF state of the
light-emitting device (LEDR). The charge control device 92 (charge
control IC) may be implemented by an integrated circuit device or
the like. The battery 94 may be provided with the function of the
charge control device 92 (e.g., smart battery). Note that the
actual load 90 is not limited to a secondary battery. For example,
a given circuit may serve as an actual load when the circuit
operates.
Secondary-Side Instrument Approach Detection and Coil
Positioning
FIG. 4 is a view showing the configuration of the power
transmitting device for secondary-side instrument approach
detection and automatic coil positioning. FIG. 4 shows the internal
configuration of the power transmitting device 10 shown in the FIG.
2 in detail.
In FIG. 4, the waveform detection circuit 28 is a peak-hold
circuit. The waveform detection circuit 28 outputs a peak voltage
SR of the coil end voltage. The peak voltage SR may be utilized for
detecting the approach of the secondary coil L2. The peak voltage
SR is compared with a first threshold value (approach detection
threshold value) V1 by the comparator CP1. An output signal PE1
from the comparator CP1 is supplied to the power-transmitting-side
control circuit 22.
The harmonic detection circuit 25 includes the filter circuit 27
that filters a voltage signal from the waveform monitoring circuit
14, the mixer 29 that adds an odd-order harmonic (fifth-order
harmonic in this example) fs of the primary coil L1, and the
detection circuit (waveform detection circuit) 31.
When the resonance frequency of the primary-side series resonant
circuit formed by the primary coil L1 and the capacitor C1 is
referred to as fp, the drive frequency of the primary coil is
generally set at a frequency (fd) away from the resonance frequency
(fp) taking operational stability into consideration. When the
drive signal of the primary coil is a symmetrical
alternating-current signal, the harmonic (fs) of the drive
frequency of the primary coil is only an odd-order harmonic. The
fifth-order harmonic (fs=5fd) may be used to detect the position of
the secondary coil, for example.
The detection output from the harmonic detection circuit 25 is
compared with a second threshold value (harmonic resonance peak
detection threshold value) V2 by the comparator CP2. An output
signal PE2 from the comparator CP2 is supplied to the
power-transmitting-side control circuit 22.
The power-transmitting-side control circuit 22 detects the approach
of the secondary-side instrument (secondary coil L2) based on the
output signal (PE1) from the comparator CP1. The
power-transmitting-side control circuit 22 transmits a primary coil
(primary-side instrument) scan instruction to the actuator control
circuit 37 using the output signal (PE2) from the comparator CP2 as
an index. The actuator control circuit 37 drives the actuator in
response to the scan instruction from the power-transmitting-side
control circuit 22. Note that the output signal (PE2) from the
comparator CP2 may be input to the actuator control circuit 37 so
that the actuator is driven based on a determination by the
actuator.
As shown in FIG. 4 (upper right), the secondary coil (L2) is
provided with the harmonic resonant capacitor C2 and the magnetic
material FS. The magnetic material FS is a shield that separates a
magnetic flux from a circuit, or may be a core of the secondary
coil, for example. The primary-side instrument can detect the
approach of the secondary coil due to the presence of the magnetic
material FS (described later in detail).
Secondary Coil Approach Detection Principle
The secondary coil approach detection principle is described below
with reference to FIGS. 5 to 7. FIGS. SA to 5F are views
illustrative of an increase in inductance that occurs when a
magnetic material attached to the secondary coil has approached the
primary coil. The term "inductance" used herein refers to an
inductance (more accurately an apparent inductance) that changes
due to the approach of the secondary coil provided with a magnetic
material, as described above. The term "apparent inductance" is
distinguished from the inductance (self-inductance) of the primary
coil (i.e., the inductance of the primary coil when the primary
coil is not affected by the secondary coil). In the following
description, the apparent inductance is indicated by Lps.
As shown in FIG. SA, the magnetic material (FS) is attached to the
secondary coil L2. As shown in FIG. 5B, the magnetic material (FS)
is a magnetic material used as a magnetic shielding material
provided between the secondary coil L2 (i.e., planar coil) and a
circuit board 3100, for example. Note that the magnetic material
(FS) is not limited thereto, but may be a magnetic material used as
a core of the secondary coil L2.
FIG. 5D shows an equivalent circuit of the primary coil L1 shown in
FIG. 5C. The resonance frequency of the primary coil L1 is fp.
Specifically, the resonance frequency is determined by the primary
coil L1 and the capacitor C1. As shown in FIG. 5E, when the
secondary coil L2 has approached the primary coil L1, the magnetic
material (FS) attached to the secondary coil L1 is coupled to the
primary coil L1. Therefore, the magnetic flux of the primary coil
(L1) passes through the magnetic material (FS) (see FIG. 5F) so
that the magnetic flux density increases. As a result, the
inductance of the primary coil L1 increases. In this case, the
resonance frequency of the primary coil L1 is fsc, as shown in FIG.
5E. Specifically, the resonance frequency is determined by the
apparent inductance Lps (i.e., the apparent inductance of the
primary coil for which the approach of the secondary coil is taken
into consideration) and the primary-side resonant capacitor C1. The
apparent inductance Lps of the primary coil is expressed by
Lps=L1+.DELTA.L (where, L1 is the inductance (self-inductance) of
the primary coil, and .DELTA.L is an increase in inductance due to
the approach of the magnetic material FS to the primary coil). A
specific value of the apparent inductance Lps may be acquired by
measuring the inductance of the primary coil when the secondary
coil has approached the primary coil using a measuring instrument,
for example.
A change in the inductance of the primary coil due to the approach
of the secondary coil is discussed below.
FIGS. 6A to 6D are views showing examples of the relative
positional relationship between the primary coil and the secondary
coil. In FIGS. 6A to 6D, PA1 indicates the center of the primary
coil L1, and PA2 indicates the center of the secondary coil L2.
In FIG. 6A, since the secondary coil L2 is positioned away from the
primary coil L1, the primary coil L1 is not affected by the
secondary coil L2. When the secondary coil (L2) has approached the
primary coil (L1), as shown in FIG. 6B, the inductance of the
primary coil L1 increases, as described with reference to FIGS. 5E
and 5F. In FIG. 6C, mutual induction (i.e., an effect that cancels
a magnetic flux of one coil by a magnetic flux of the other coil)
occurs due to coupling of the primary coil (L1) and the secondary
coil (L2) in addition to self-induction.
When the position of the secondary coil (L2) has coincided with the
position of the primary coil (L1) (see FIG. 6D), a current flows
through the secondary coil (L2). As a result, a leakage magnetic
flux decreases due to cancellation of the magnetic flux as a result
of mutual induction so that the inductance of the coil decreases.
Specifically, the secondary-side instrument starts to operate as a
result of positioning. A current flows through the secondary coil
(L2) due to the operation of the secondary-side instrument so that
a leakage magnetic flux decreases due to cancellation of the
magnetic flux as a result of mutual induction, whereby the
inductance of the primary coil (L1) decreases.
FIG. 7 is a view showing the relationship between the relative
distance between the primary coil and the secondary coil and the
inductance of the primary coil. In FIG. 7, the horizontal axis
indicates the relative distance, and the vertical axis indicates
the inductance. The term "relative distance" used herein refers to
a relative value obtained by normalizing the distance between the
centers of the two coils in the horizontal direction. The relative
distance is an index that indicates the distance between the coils
in the horizontal direction. An absolute distance (e.g., an
absolute value (mm) that indicates the distance between the centers
of the coils in the horizontal direction) may be used instead of
the relative distance.
In FIG. 7, when the relative distance is d1, the primary coil L1 is
not affected by the secondary coil. In this case, the inductance of
the primary coil L1 is "a" (i.e., the self-inductance of the
primary coil). When the secondary coil L2 has approached the
primary coil L1 (relative distance: d2), the magnetic flux density
increases due to the magnetic material so that the inductance of
the primary coil L1 increases to "b".
When the secondary coil L2 has further approached the primary coil
L1 (relative distance: d3), the inductance of the primary coil L1
increases to "c". When the secondary coil L2 has further approached
the primary coil L1 (relative distance: d4), the inductance of the
primary coil L1 increases to "d". The primary coil L1 and the
secondary coil L2 are coupled in this state so that the effect of
mutual inductance becomes predominant.
Specifically, when the relative distance is d5, since the effect of
mutual inductance becomes predominant, the inductance of the
primary coil L1 then decreases to "e". When the relative distance
is 0 (i.e., the centers of the primary coil and the secondary coil
are positioned at the center of the XY plane), a leakage magnetic
flux is minimized due to cancellation of the magnetic flux so that
the inductance of the primary coil L1 converges to a constant value
("center inductance" in FIG. 7).
The relative distance d2 is the power transmission limit range. In
this case, it is possible to detect that the secondary coil (L2)
has approached the primary coil L1 up to the relative distance d2
using an inductance threshold value (INth1).
Specifically, when an increase in inductance due to the approach of
the secondary coil (L2) has been detected using the first
inductance threshold value (INth1), the secondary coil L2 has
approached the primary coil L1 to such an extent that the relative
distance is almost within the power transmission range.
Note that the approach of the secondary coil is actually determined
using a voltage threshold value (first threshold value V1)
corresponding to the inductance threshold value (INth1).
In this embodiment, the power transmitting section 12
intermittently (e.g., cyclically) drives the primary coil (L1) in
order to automatically detect the approach of the secondary coil
(L2). This enables automatic detection of the approach of the
secondary coil (secondary-side instrument).
When the approach of the secondary coil (L2) has been detected, a
secondary coil position detection operation utilizing harmonic
resonance is performed.
The details are described below.
Principle of Detecting Relative Positional Relationship Between
Primary Coil and Secondary Coil Utilizing Harmonic Resonance
FIG. 8 is a view illustrative of the concept of a leakage
inductance in a transformer formed by electromagnetically coupling
the primary coil and the secondary coil. The upper part of FIG. 8
shows the state of a magnetic flux between the coils disposed
adjacently, and the lower part of FIG. 8 shows an equivalent
circuit of the transformer.
In FIG. 8, the primary coil (L1) and the secondary coil (L2) are
circular coils having a radius of R. When a magnetic flux .phi.A
generated from the primary coil (L1) is interlinked to the
secondary coil (L2), a current flows through the secondary coil
(L2) due to mutual induction to cancel the magnetic flux of the
primary coil (L1) so that the magnetic flux apparently becomes
zero. Specifically, the mutual inductance M of the transformer
ideally becomes zero.
However, a leakage magnetic flux .phi.B exists in the primary coil
(L1), and a leakage magnetic flux .phi.C exists in the secondary
coil (L2). A primary-side leakage inductance LQ occurs due to the
primary-side leakage magnetic flux .phi.B, and a secondary-side
leakage inductance LT occurs due to the secondary-side leakage
magnetic flux .phi.C. It is considered that an ideal transformer
exists in theory. However, it is not related to the leakage
inductance model and may be disregarded.
FIGS. 9A to 9E are views illustrative of the configuration and the
operation of a harmonic resonant circuit. As shown in FIG. 9A, the
harmonic resonant capacitor C2 is connected to the secondary coil
(L2). FIG. 9B show an equivalent circuit of the transformer in this
case. The secondary-side load (RL) is not connected before power
transmission. Since the mutual inductance is substantially zero, as
described above, the mutual inductance can be disregarded. Since
the primary-side leakage inductance (LQ) and the secondary-side
leakage inductance (LT) are connected in series, the composite
inductance of the primary-side leakage inductance (LQ) and the
secondary-side leakage inductance (LT) is (LQ+LT). Therefore, the
equivalent circuit of the transformer can be modified as shown in
FIG. 9C.
As shown in FIG. 9C, two resonant circuits SY1 and SY2 are formed.
The following description focuses only on the resonant circuit SY2
while disregarding the resonant circuit SY1. FIG. 9D shows
odd-order harmonics of the drive frequency (fd) of the drive signal
(VD) of the primary coil (L1). The following description focuses on
the fifth-order harmonic (5fd) (note that the harmonic is not
limited thereto; the third-order harmonic, the seventh-order
harmonic, or the like may also be used).
In this embodiment, the capacitance of the capacitor C2 is set so
that the resonance frequency fs of the resonant circuit SY2
coincides with the fifth-order harmonic (5fd) of the drive
frequency of the primary coil (L1), as indicated by an expression
shown in FIG. 9E. Therefore, the resonant circuit SY2 is a harmonic
resonant circuit that resonates with the fifth-order harmonic of
the drive frequency of the primary coil. Therefore, the equivalent
circuit shown in FIG. 9C has resonance characteristics shown in
FIG. 9E. The harmonic resonance peak is obtained at a position 5fd
on the frequency axis. In this case,
fs=5fd=1/{2.pi.(LQ+LT)C2)}.sup.1/2 is satisfied. In the above
expression, fs indicates the resonance frequency, and 5fd indicates
the fifth-order harmonic.
As described above, a leakage inductance is an inductance produced
by a leakage magnetic flux that does not undergo interlinkage. The
amount of leakage magnetic flux differs depending on the relative
positional relationship between the primary coil (L1) and the
secondary coil (L2).
Therefore, when the capacitance of the capacitor C2 of the harmonic
resonant circuit SY2 described with reference to FIG. 9 is set
taking into account the leakage inductance when the position of the
primary coil coincides with the position of the secondary coil, the
harmonic resonant circuit SY2 undergoes harmonic resonance when the
position of the primary coil coincides with the position of the
secondary coil, for example. When the capacitance of the capacitor
C2 is set taking into account the leakage inductance when the
primary coil and the secondary coil are positioned at a given
distance R, the harmonic resonant circuit SY2 undergoes harmonic
resonance when the primary coil (L1) and the secondary coil (L2)
are positioned at the given distance R.
FIGS. 10A and 10B are views illustrative of a harmonic resonant
circuit that resonates when the primary coil and the secondary coil
are positioned at the given distance R. As shown in FIG. 10A, when
the capacitance of the capacitor C2 is set taking into account the
leakage inductances (.phi.B and .phi.C) when the distance between
the center of the primary coil (L1) and the center of the secondary
coil (L2) is R, the harmonic resonant circuit SY2 undergoes
harmonic resonance when the primary coil (L1) and the secondary
coil (L2) are positioned at a given distance R.
As shown in FIG. 10B, when the leakage inductances when the primary
coil (L1) and the secondary coil (L2) are positioned at the given
distance R are referred to as LQ(R) and LT(R), the harmonic
resonant circuit SY2 is caused to undergo harmonic resonance when
the primary coil (L1) and the secondary coil (L2) are positioned at
the given distance R by setting the capacitance of the capacitor C2
to satisfy the expression shown in FIG. 10B.
FIGS. 11A to 11D are views illustrative of a position at which the
harmonic resonance peak is obtained when scanning the primary coil
with respect to the secondary coil. As shown in FIG. 11A, the
center of the primary coil (L1) is referred to as PA1, and the
center of the secondary coil (L2) is referred to as PA2.
As shown in FIG. 11A, the primary coil (L1) is scanned linearly
from the left toward the secondary coil (L2). In this case, the
harmonic resonance peak is obtained when the primary coil (L1)
approaches the secondary coil (L2) so that the distance between the
primary coil (L1) and the secondary coil (L2) is R, as shown in
FIG. 11B. The harmonic resonance peak is also obtained when the
primary coil (L1) moves away from the secondary coil (L2), as shown
in FIG. 11C.
When the primary coil (L1) is scanned along an arbitrary axis that
intersects the secondary coil (L2) in a stationary state, the
resonance peak is obtained at a position on a circumference at a
distance R from the center PA2 of the secondary coil (L2), as shown
in FIG. 11D. Specifically, when a position at which the harmonic
resonance peak is obtained is referred to as W, the position W
coincides with the outermost circle of the secondary coil (L2).
FIG. 12 is a view showing an example of a change in the inductance
of the primary coil and an example of a change in the harmonic
voltage obtained from the harmonic detection circuit when the
primary coil approaches the secondary coil. The upper part of FIG.
12 is the same as FIG. 7.
As shown in the lower part of FIG. 12, the harmonic resonance peak
is obtained by the harmonic detection circuit 25 when the distance
between the primary coil and the secondary coil is R (=relative
distance d5). Therefore, the harmonic peak can be detected by
comparing the output from the harmonic detection circuit 25 with a
harmonic peak detection threshold voltage (V2).
As described with reference to FIG. 7, the approach of the
secondary coil can be detected by a decrease in coil end voltage
(coil current) due to an increase in the inductance of the primary
coil when the distance between the center of the primary coil and
the center of the secondary coil is L (=relative distance d2).
As shown in FIG. 12, the distance R (distance at which the harmonic
resonance peak occurs) is shorter than the distance L (approach
detection distance) (R<L). Specifically, a situation in which
the secondary coil has approached the primary coil within the
distance L is detected by approach detection, and a situation in
which the primary coil and the secondary coil have been positioned
at the distance R is detected by the harmonic detection.
Note that the distance R (distance at which the harmonic resonance
peak occurs) may be zero (R=0). Specifically, when harmonic
resonance has occurred when R=0 (i.e., when the position of the
primary coil coincides with the position of the secondary coil),
the primary coil and the secondary coil can be positioned by moving
the primary-side instrument by trial and error using the harmonic
peak as an index, or the primary coil and the secondary coil can be
positioned by manually moving the secondary-side instrument.
Moreover, placement or removal (leave) of the secondary-side
instrument can be detected depending on the presence or absence of
the harmonic peak.
FIGS. 13A and 13B are views illustrative of a harmonic resonant
circuit that resonates when the position of the primary coil
coincides with the position of the secondary coil. As shown in FIG.
13A, when the capacitance of the capacitor C2 is set taking into
account the leakage inductances (.phi.B and .phi.C) when the center
of the primary coil (L1) coincides with the center of the secondary
coil (L2, the harmonic resonant circuit SY2 undergoes harmonic
resonance when the position of the primary coil (L1) coincides with
the position of the secondary coil (L2).
As shown in FIG. 13B, when the leakage inductances when the
position of the primary coil coincides with the position of the
secondary coil are referred to as LQ(0) and LT(0), the harmonic
resonant circuit SY2 undergoes harmonic resonance when the position
of the primary coil (L1) coincides with the position of the
secondary coil (L2) by setting the capacitance of the capacitor C2
to satisfy the expression shown in FIG. 13B.
Scanning Primary Coil Using Harmonic Detection Output as Index
FIGS. 14A and 14B are views illustrative of a primary coil
positioning method that scans the primary coil by trial and error
using the detection output from the harmonic resonant circuit as an
index. The primary coil may be moved by trial and error by moving
the primary coil based on a given movement sequence (e.g., based on
a spiral scan sequence), or moving the primary coil at random, for
example. The following description is given taking an example in
which the primary coil is scanned spirally (note that various scan
patterns such as a zigzag scan may also be employed).
As shown in FIG. 14A, the power transmitting device 10 including
the primary coil (L1) is placed on the XY stage 702. In FIG. 30A,
PA1 indicates the center of the primary coil.
When the power-transmitting-side control circuit 22 included in the
power transmission control device 20 has detected placement of the
secondary-side instrument by the above-described approach
detection, the power-transmitting-side control circuit 22 causes
the actuator control circuit 37 to move the XY stage 702 so that
the primary coil L1 is scanned spirally, as shown in FIG. 14B.
Specifically, the primary coil is gradually moved so that the
center PA1 of the primary coil L1 draws a spiral. The
power-transmitting-side control circuit 22 determines whether or
not the output level of the harmonic detection circuit 25 has
exceeded the threshold voltage V2 using the comparator CP2 while
moving the primary coil L1. The power-transmission-side control
circuit 22 stops scanning the primary coil (L1) when the output
level of the harmonic detection circuit 25 has exceeded the
threshold voltage V2.
Specifically, if the harmonic resonant circuit (SY2 in FIG. 9)
formed in the secondary-side instrument resonates when the position
of the primary coil (L1) coincides with the position of the
secondary coil (L2), for example, the position of the primary coil
(L1) should coincide with the position of the secondary coil (L2)
when the output level of the harmonic detection circuit 25 has
exceeded the threshold voltage V2. This means that the primary coil
(L1) has been positioned with respect to the secondary coil
(L2).
The primary coil (L1) can thus be automatically positioned by
scanning the primary coil (L1) using the harmonic detection output
as an index. FIG. 15 shows a summary of the above-described
process.
FIG. 15 is a flowchart showing the process of scanning the primary
coil using the harmonic detection output as an index. The
power-transmitting-side control circuit 22 intermittently (e.g.,
cyclically) drives the primary coil at the drive frequency fd in
order to automatically detect placement of the secondary-side
instrument (i.e., the approach of the secondary coil) (step S1),
and detects the approach of the secondary coil by detecting a
decrease in coil end voltage (coil current) due to an increase in
inductance (step S2).
When the power-transmitting-side control circuit 22 has detected
placement of the secondary-side instrument by the above-described
approach detection, the power-transmitting-side control circuit 22
causes the actuator control circuit 37 to move the XY stage 702 so
that the primary coil is scanned spirally, for example (step S3),
and determines whether or not the harmonic detection output level
has exceeded the given threshold voltage (i.e., whether or not the
desired positional relationship has been achieved) while scanning
the primary coil (step S4). When the primary coil and the secondary
coil have satisfied the desired positional relationship, the
power-transmission-side control circuit 22 stops scanning (spirally
scanning) the primary coil.
Configuration Example and Operation of XY Stage
An example of the configuration of the XY stage and the operation
of the XY stage are described below. FIG. 16 is a perspective view
showing the basic configuration of the XY stage.
As shown in FIG. 16, the XY stage 702 includes a pair of guide
rails 100, an X-axis slider 200, and a Y-axis slider 300. Aluminum,
iron, granite, a ceramic, or the like is used as the material for
these members.
The guide rails 100 respectively have guide grooves 110 opposite to
each other. The guide rails 100 extend in parallel in the X-axis
direction. The guide rails 100 are secured on a surface plate (not
shown).
The X-axis slider 200 engages the guide rails 100. The X-axis
slider 200 is in the shape of a rectangular flat plate. The ends of
the X-axis slider 200 are fitted into the guide grooves 110 so that
the X-axis slider 200 can be moved in the X-axis direction along
the guide grooves 110, but cannot be moved in the Y-axis direction.
Therefore, the X-axis slider 200 can be reciprocated in the X-axis
direction along the guide rails 100.
Note that the guide groove 10 formed in the guide rail 100 may be
formed in the X-axis slider 200, and the guide rail 100 may have a
protrusion that is fitted into the guide groove formed in the
X-axis slider 200. It suffices that the engagement portion of the
guide rail 100 and the X-axis slider 200 be supported on three
sides. The shape of the guide groove is not particularly
limited.
The Y-axis slider 300 is provided to enclose the X-axis slider 200.
The Y-axis slider 300 has a cross-sectional shape (almost in the
shape of the letter U) corresponding to the cross-sectional shape
of the X-axis slider 200 in the shape of a rectangular flat
plate.
The end of the Y-axis slider 300 almost in the shape of the letter
U is bent inward. The upper part of the Y-axis slider 300 may be
open. Alternatively, the Y-axis slider 300 may have a
cross-sectional shape having no opening.
The ends of the X-axis slider 200 in the widthwise direction that
engage the guide grooves 110 are thus supported by the Y-axis
slider 300 on the upper side, the side, and the lower side. Since
the Y-axis slider 300 is secured on the X-axis slider 200, the
movement of the Y-axis slider 300 in the X-axis direction with
respect to the X-axis slider 200 is prevented. When the X-axis
slider 200 is moved in the X-axis direction, the Y-axis slider 300
moves in the X-axis direction together with the X-axis slider
200.
The Y-axis slider 300 can be moved in the Y-axis direction with
respect to the X-axis slider 200. The X-axis slider 200 functions
as an X-axis direction moving member, and also serves as a guide
that allows the Y-axis slider 300 to move in the Y-axis direction
with respect to the X-axis slider 200. The upper part of the Y-axis
slider 300 serves as a top plate (movable main surface) on which an
object that is moved along the XY axes is placed.
As shown in FIG. 16, the power transmission device 10 including the
primary coil (circular wound coil) L1 and the power transmission
control device 20 (IC) is provided on the main surface (top plate)
of the Y-axis slider 300. When the primary coil L1 is a wound coil,
the volume and the height of the coil can be reduced. This is
advantageous when scanning the primary coil L1. Note that the type
of the primary coil is not limited to the above-described
example.
The XY stage 702 shown in FIG. 16 utilizes a highly accurate linear
motor as a drive source. A ball screw mechanism may be used instead
of the linear motor.
An X-axis linear motor 600 that moves the X-axis slider 200 is
provided between the pair of guide rails 100. A movable member 620
of the X-axis linear motor 600 secured on a rod-shaped stator 610
is secured on the lower part of the X-axis slider 200 so that the
X-axis slider 200 can be reciprocated.
The Y-axis slider 300 is reciprocated by a Y-axis linear motor 700.
A depression 210 is formed in the X-axis slider 200, and the Y-axis
linear motor is placed in the depression 210. Therefore, the stage
height can be reduced.
The X-axis linear motor 600 and the Y-axis linear motor 700
respectively correspond to the X-direction actuator 720 and the
Y-direction actuator 730 shown in FIG. 2.
The power-transmitting-side device (i.e., the primary-side
structure of the non-contact power transmission system) 704 is
formed by placing the power transmission device 10 including the
primary coil (circular wound coil) L1 and the power transmission
control device 20 (IC) on the XY stage 702.
As shown in FIG. 1B, the power-transmitting-side device 704 is
provided in a structure (e.g., desk) having a flat surface, for
example. This implements the power-transmitting-side device 704
that deals with a next-generation non-contact power transmission
system capable of automatically moving the position of the primary
coil in the XY plane corresponding to the position of a secondary
coil of a secondary-side instrument (e.g., portable terminal)
placed at an approximate position.
As described above, the power transmission control device 20
according to this embodiment intermittently drives the primary
coil, and always monitors whether or not the coil end voltage
(current) has decreased due to an increase in primary-side
inductance. When the approach of the secondary-side instrument
(i.e., the secondary-side instrument has been placed in a given
area Z1) has been detected, the actuator control circuit 37
automatically adjusts the position of the primary coil.
Since the secondary-side instrument approach detection process and
the primary coil position adjustment process are automatically
performed, the user's workload is reduced. Note that the approach
detection process may not be performed, or the position of the
primary coil may be manually adjusted.
Second Embodiment
In this embodiment, the primary-side instrument is not provided
with the primary coil scan mechanism using the actuator. The user
positions the primary coil and the secondary coil by manually
moving the secondary-side instrument. The details are described
below.
FIG. 17 is a view showing another configuration of the power
transmitting device (configuration that detects the approach of the
secondary-side instrument and notifies the user of coil relative
positional relationship information). The main configuration shown
in FIG. 17 is the same as that shown in FIG. 4. The power
transmitting device shown in FIG. 17 differs from that shown in
FIG. 4 in that a display control section 39 is provided instead of
the actuator control circuit 37.
Specifically, a power transmitting device 10 shown in FIG. 17
(power transmission control device 20) merely has a function of
notifying the user of a detection result (relative positional
relationship information) for the relative positional relationship
between the primary coil and the secondary coil based on the
harmonic detection output of the harmonic detection circuit 25
using the display section 16. The power transmitting device 10 may
notify the user of the detection result using sound or the
like.
FIGS. 18A and 18B are views showing an example of an application of
a non-contact power transmission system using the power
transmitting device having a configuration shown in FIG. 17. FIG.
18A is a perspective view showing a system desk, and FIG. 18B is a
cross-sectional view of the system desk shown in FIG. 18A along the
line P-P'.
As shown in FIG. 18B, the power transmitting device 10 is provided
in a structure (system desk in this example) 620 having a flat
surface. Specifically, the power transmitting device 10 is provided
in a depression formed in the system desk 620. A flat plate (flat
member; e.g., an acrylic plate having a thickness of several
millimeters) 600 is provided over (on the upper side of) the system
desk 620. The flat plate 600 is supported by a support member
610.
A display section (LED) 16 is provided on the flat plate 600. The
user is notified of a detection result (relative positional
relationship information) for the relative positional relationship
between the primary coil and the secondary coil based on the
harmonic detection output using the display section (LED) 16. For
example, the display section (LED) 16 emits red light when the
position of the primary coil (L1) has coincided with the position
of the secondary coil (L2), and is turned OFF when the position of
the primary coil (L1) does not coincide with the position of the
secondary coil (L2).
The flat plate 600 includes a portable terminal placement area Z1
in which a portable terminal (including a portable telephone
terminal, a PDA terminal, and a portable computer terminal) is
placed. As shown in FIG. 18A, the portable terminal placement area
Z1 included in the flat plate 600 differs in color from the
remaining area so that the user can determine that the portable
terminal placement area Z1 is an area in which a portable terminal
should be placed. Note that the color of the boundary area between
the portable terminal placement area Z1 and the remaining area may
be changed instead of changing the color of the entire portable
terminal placement area Z1.
A portable terminal (secondary-side instrument) 510 includes a
power receiving device 40 (including a secondary coil) that
receives power transmitted from the power transmitting device
10.
When the portable terminal 510 has been placed at an approximate
position in the portable terminal placement area Z1, the power
transmitting device 10 provided in the system desk 620
automatically detects placement of the portable terminal 510. This
allows the power transmitting device 10 to detect the relative
positional relationship between the primary coil and the secondary
coil based on the harmonic detection output and display the
detection result.
The user manually moves the portable terminal 510, and checks
whether or not the display section (LED) 16 emits light. The user
stops moving the portable terminal 510 when the display section
(LED) 16 has emitted light. The secondary coil (L2) is thus
positioned with respect to the primary coil (L1).
As described above, the secondary coil (L2) can be positioned with
respect to the primary coil (L1) by providing the display section
(LED) 16 that emits light of a given color when a harmonic
detection output that exceeds a given level is obtained, and
manually moving the portable terminal 510 (i.e., secondary-side
instrument) by trial and error to search for a position at which
the display section (LED) 16 emits light.
The power transmitting device 10 then starts a given operation for
power transmission. When power transmission has started, the
display section (LED) 16 emits yellow light to notify the user that
power transmission (charging) is performed, for example.
The user may be notified of the relative positional relationship
information using the display section (LED) 16 in various ways. For
example, a multi-stage notification operation may be performed
corresponding to the level of the harmonic detection output as a
coil relative positional relationship detection signal. For
example, the display section (LED) 16 emits red light when a
harmonic detection output that exceeds a first level is obtained,
and emits green light when a harmonic detection output that exceeds
a second level higher than the first level is obtained.
The user manually moves the portable terminal 510 (secondary-side
instrument) by trial and error, and checks whether or not the
display section (LED) 16 emits light and the color of the light.
This makes it possible to more efficiently position the secondary
coil (L2) with respect to the primary coil (L1).
Specifically, since the secondary coil (L2) has approached the
primary coil (L1) to some extent when the display section (LED) 16
emits red light, the user can more carefully move the
secondary-side instrument 510 (portable terminal) within a narrow
search (movement) range.
According to this example, the secondary-side instrument 510
(portable terminal) can be easily positioned utilizing color
display. This makes it easy to position the secondary coil (L2)
with respect to the primary coil (L1).
Note that the user may be notified of placement or removal (leave)
of the secondary-side instrument 510 (portable terminal) utilizing
the state (e.g., ON, OFF, or the color of the light) of the display
section (LED) 16.
Third Embodiment
The above embodiments have been described taking an example in
which the harmonic detection circuit 25 and the secondary coil
approach detection circuit (28 or CP1) function as a means for
adjusting the positional relationship between the primary coil (L1)
and the secondary coil (L2). These circuits also function as a
means that detects (determines) whether or not an article placed in
the placement area (Z1) can be a power transmission target.
Specifically, when a harmonic can be detected by the harmonic
detection circuit 25, the article placed in the placement area is
not a screw, a nail, or the like, but is a secondary-side
instrument that can be (may be) a power transmission target.
Specifically, the harmonic detection circuit 25 also has a function
of a means that detects whether or not the article placed in the
placement area (Z1) is an instrument that can be a power
transmission target (i.e., a detector that detects whether or not
the article is an appropriate secondary-side instrument).
Likewise, when the approach of the secondary coil can be detected
by the secondary coil approach detection circuit (28 or CP1), the
secondary-side instrument that can be a power transmission target
approaches. Therefore, the approach detection circuit also has a
function of a means that detects whether or not the instrument
placed in the placement area (Z1) is a secondary-side instrument
that includes the secondary coil and can be a power transmission
target (i.e., a detector that detects whether or not the instrument
is an appropriate secondary-side instrument).
According to this embodiment, the primary-side instrument can
easily and independently detect whether or not the article placed
in the placement area can be a power transmission target (i.e., can
determine whether or not the secondary-side instrument is
appropriate) (by a simple configuration utilizing the function of
the non-contact power transmission).
If the primary-side instrument can independently determine whether
or not the article placed in the placement area can be a power
transmission target, a situation in which power is unnecessarily
transmitted to an article that cannot be a power transmission
target is prevented. Therefore, unnecessary power consumption and
heat generation can be prevented.
In the above-described example, the primary-side instrument
independently detects the secondary coil position and the like.
Note that the invention is not limited thereto. For example, the
secondary-side instrument may transmit an index signal to the
primary-side instrument, and the primary-side instrument may
receive the index signal and determine the secondary coil
position.
The secondary-side instrument may transmit self-ID information, and
the primary-side instrument may receive the self-ID information and
determine that the secondary-side instrument is a power
transmission target.
In the configuration shown in FIGS. 18A and 18B, the display
section 16 (notification section) may notify the user whether or
not the article placed in the placement area Z1 is an instrument
that can be a power transmission target (e.g., a secondary-side
instrument having a secondary-side configuration compliant with the
standard), for example. For example, when the reception level of
the harmonic detection circuit is appropriate, the article placed
in the placement area Z1 is determined to be a secondary-side
instrument that can be a power transmission target, and the display
section 16 emits green light. This enables the user to determine
that utilization of the non-contact power transmission system has
been allowed.
Fourth Embodiment
In this embodiment, the placement area Z1 shown in FIG. 1A is
formed using a transparent member (including a translucent member).
The area other than the placement area may be formed using an
opaque member (or a member that differs in light reflectance from
the placement area).
In this case, since the user can determine the placement area Z1
and visually observe the lower side (inside) of the placement area
Z1, the user can easily determine the position of a primary coil
(L1) provided under (in) the placement area Z1 either directly or
indirectly.
For example, the user may visually observe the primary coil (L1).
Alternatively, the primary coil (L1) may be covered with an IC
package or the like, and a mark that indicates the coil position
may be attached to the IC package or the like. In this case, the
user can determine the position of the primary coil (L1) using the
mark as an index.
Therefore, when the user moves the position of the secondary-side
instrument to position the primary coil (L1) and the secondary coil
(L2) (second embodiment), the user can more easily position the
primary coil (L1) and the secondary coil (L2) so that the
convenience to the user is improved.
Although only some embodiments of the invention have been described
in detail above, those skilled in the art would readily appreciate
that many modifications are possible in the embodiments without
materially departing from the novel teachings and advantages of the
invention. Specifically, various modifications are possible without
materially departing from the novel teachings and advantages of the
invention.
Accordingly, such modifications are intended to be included within
the scope of the invention. Any term (e.g., GND and portable
telephone) cited with a different term (e.g., low-potential-side
power supply and electronic instrument) having a broader meaning or
the same meaning at least once in the specification and the
drawings can be replaced by the different term in any place in the
specification and the drawings. The coil includes a coil formed by
a wire provided in a semiconductor substrate. Any combinations of
the embodiments and the modifications are also included within the
scope of the invention.
The configurations and the operations of the power transmission
control device, the power transmitting device, the power reception
control device, and the power receiving device, and the method of
detecting the secondary-side load by the primary side instrument
are not limited to those described in the above embodiments.
Various modifications and variations may be made.
(1) According to at least one aspect of the invention, the
following effects can be obtained, for example. Note that the
following effects are not necessarily achieved at the same time.
Accordingly, the following effects do not in any way limit the
scope of the invention.
(2) The power transmitting device (primary-side instrument) can
voluntarily and accurately detect the relative positional
relationship between the power transmitting device (primary-side
instrument) and the power receiving device (secondary-side
instrument).
(3) A novel coil relative positional relationship detection method
utilizing the resonance of the odd-order harmonic of the drive
frequency of the primary coil is implemented.
(4) A situation in which the primary coil and the secondary coil
are positioned to satisfy a given relationship (e.g., the position
of the primary coil coincides with the position of the secondary
coil, or the primary coil and the secondary coil are positioned at
the given distance R) can be detected by adjusting the circuit
parameter of the harmonic resonant circuit provided in the
secondary-side instrument.
(5) The primary coil and the secondary coil can be automatically
positioned by automatically scanning the primary coil using the
actuator and the XY stage utilizing the position detection result
based on the harmonic detection output as an index.
(6) The user can position the secondary-side instrument by moving
the secondary-side instrument by trial and error using the position
detection result based on the harmonic detection output as an
index.
(7) Placement or removal (leave) of the secondary-side instrument
in or from a given area can be detected based on the harmonic
detection output.
The positioning operation can be completely automated by combining
the technology that allows the primary-side instrument to
automatically detect the approach of the secondary coil provided
with a magnetic material and the automatic primary coil positioning
technology using the actuator.
(8) Since appropriate power transmission is necessarily implemented
regardless of the size, shape, design, and the like of the
secondary-side instrument, the versatility of the non-contact power
transmission system is significantly improved.
(9) Since the degree of freedom of the design of the secondary-side
instrument is not limited, a burden is not imposed on the
manufacturer of the secondary-side instrument.
(10) Since the relative positional relationship between the coils
is detected by effectively utilizing the circuit configuration of
the non-contact power transmission system without using a special
circuit (e.g., position detection element), the configuration does
not become complicated.
(11) For example, a highly versatile and convenient next-generation
non-contact power transmission system can be implemented that
enables the position of the primary coil to be automatically
adjusted to enable charging or the like merely by placing a
portable terminal or the like in a given area of a structure (e.g.,
desk) having a flat surface, or enables the primary coil and the
secondary coil to be positioned by manually moving a portable
terminal or the like.
(12) Whether or not the article placed in the placement area is a
secondary-side instrument that includes the secondary coil and can
be a power transmission target can be detected using the harmonic
detection circuit and the secondary coil approach detection
circuit, and the user can be notified of the detection result using
the notification means.
The invention achieves an effect of providing a next-generation
non-contact power transmission system with significantly improved
versatility and convenience. Therefore, the invention is useful for
a power transmission control device (power transmitting control
IC), a power transmitting device (e.g., IC module), a non-contact
power transmission system, a secondary coil positioning method, and
the like.
* * * * *